The effects of nutritional deficits on reproductive behavior are very important for a number of reasons. In society today, some people are fasting and dieting, even though food is plentiful and they can afford to eat a balanced diet. In other socioeconomic classes or in other countries (e.g., developing nations), food is scarce. Dietary restrictions can have a major impact on reproductive behavior particularly for women, in that reproduction is energetically expensive. The proposal is to use an animal model (the meadow vole) to examine the effects of food deprivation on three aspects of reproductive behavior (attractivity, proceptivity, and receptivity) as well as the mechanisms (both hormonal and metabolic) that affect these behaviors. The proposal provided new insights about the various aspects of reproductive behavior since most previous studies have only examined the effects of nutritional deficiency on one aspect of receptivity, lordosis, in females. This application provides an interesting set of experiments are proposed to examine the effects of food deprivation on attractivity, proceptivity, and receptivity as well as on the metabolic and endocrine mechanisms that mediate them. The experiments tests predictions of the metabolic fuels hypothesis and the reproduction at all costs hypothesis and determine the metabolic and endocrine signals that are necessary and sufficient to maintain reproductive physiology and the components of sexual behavior in both males and females. The proposal tests hypotheses centered on 1) the effects of food deprivation on the three components of sexual behavior;2) the role of glucose utilization and lipid utilization on sexual behavior;3) changes in steroid hormone concentrations (corticosterone, testosterone, and estradiol) that accompany food deprivation;4) the role of these steroid hormones in mediating the effects of food deprivation on sexual behavior. The application is significant for its potential to expose undergraduates to research and for the new information that might be gained on the physiological regulation of sexual behavior.